The correct answers are:
A. They led to an increase in population density;
B. They made it easier to travel long distances;
C. They helped in establishing towns;
The impact that the advancements in the transportation had was enormous. It enabled the people to travel much longer distance, for much less time, much cheaper, and much safer. Because of this, the people were able to move easily towards the West. That has led to a formation of lot of new tows in the West. Very quickly, the places that were established earlier, and the new towns, got large masses of people coming in, thus becoming much bigger, and experienced much higher population density.